Fluid heater

ABSTRACT

A fluid heater, particularly adapted for use with a swimming pool, has a powered gas burner therein for supplying high intensity heat to pool water flowing in a tubular heat exchanger adjacent the burner plate. The heat exchanger is arranged in a heater housing to define therewith a flow path adjacent the tubes for the products of combustion from the burner whereby heat by convection is supplied to the tubes from the exhaust gases. The input end of the heat exchanger includes a valve member adapted to maintain a predetermined rate of flow of water through the tubes and to bypass excess water back to the pool.

United States Patent 1191 Reid, Jr. et al. [451 May 22, 1973 [54] FLUIDHEATER 3,118,430 1 1964 Russell et a] ..122 250 R Inventors: Edward A.Reid Robert G. 3,267,909 8/1966 McClanahan ..122/250 R v d l b th fc l b3,292,598 12/1966 Miller et al. ..l22/406R 3,315,646 4/1967 Witten, Jr...122/367 VR [73] Assignee: Columbia Gas System Service Corpgygflon Wili t D L Primary Examiner-Kenneth W. Sprague Filed Dec 27 1971Att0rneyHar0ld L. Stults 21 Appl. N6; 212,517 [57] ABSTRACT Related US Ali ti Data A fluid heater, lparticularly aldapteg for uze withf aSwimming poo as a powere gas urner t ere1n or [63] Contmuat1on-1n-partof Ser. No. 7,445, Feb. 2, 1970, Supplying high intensity heat to poolwater flowing in a tubular heat exchanger adjacent the burner plate. Theheat exchanger is arranged in a heater housing to 2% g "122/250 122,367i define therewith a flow path adjacent the tubes for the d 0 R 367/Rproducts of combustion from the burner whereby heat 1 0 122,367 406 byconvection is supplied to the tubes from the exhaust gases. The inputend of the heat exchanger in- [56] R f r e Cit cludes a valve memberadapted to maintain a e e we 5 e predetermined rate of flow of waterthrough the tubes UNITED STATES PATENTS and to bypassexcess water backto the pool.

2,987,259 6/1961 Lindquist ..122/250 R 17 Claims, 8 Drawing FiguresPATENIEU MAY 2: i973 SHEET 3 OF 3 FLUID HEATER This application is acontinuation-in-part of copending U.S. Pat. application Ser. No. 7,445,filed Feb. 2, 1970, now U.S. Pat. No. 3,630,175, the disclosure of whichis incorporated herein by reference.

This invention relates to fluid heaters and more in particular to aswimming pool heater having a powered gas burner for supplying highintensity heat to pool water.

In swimming pool water treatment systems presently available, water isconducted from the pool through a filtering and circulation system andis generally heated in a heater unit which forms part of the system andflow path for the water. Typically, these units utilize directblue flamenon-powered gas burners, and they are relatively inefficient in theproduction of necessary heat. As a result, the cost of operation ofconventional swimming pool heaters in order to maintain desirable watertemperatures, particularly in large pools, is inordinately high.

It is an object of this invention to provide a fluid heater unit forefficiently maintaining desired water temperatures in swimming pools. Itis another object of this invention to supply increased amounts of heatto water in a swimming pool circulation system. It is a further objectof the invention to provide a swimming pool heater wherein the volume ofwater flowing through the heater is controlled for maximum heat transferefficiency. It is a still further object of this invention to providecompact, efficient and inexpensive swimming pool water heaters.

In accordance with an aspect of this invention, a generally gas-tighthousing is provided in which an apertured base member or gas burnerplate is mounted along with a blower to form a powered gas burnersystem. A heat exchanger comprising a plurality of finned tubesinterconnected to permit liquid flow therebetween is positioned belowthe burner plate to receive the heat of combustion of gases on theburner plate. The heater is sealed so that all of the products ofcombustion flow between and around the tubes and provide additional heatby convection and conduction to the tubes prior to discharge from theheater. Deflector baffles are provided below the heat exchange tubes andbeneath the spaces between conduits to force the products of combustionpassing through the heat exchanger to contact the entire surface area ofthe tubes to provide substantially uniform convective heat thereto.

The burner plates used with the fluid heater of the present inventionare formed of a ceramic material having venturi-like apertures ororifices, as disclosed in commonly assigned copending U.S. Pat.application Ser. No. 775,978, filed Oct. 2, 1968, now abandoned, thedisclosure of which application is incorporated herein by reference.Flashback of flame through the orifices is prevented by the venturi-likeconfigurations which afford a throat portion of small cross sectionleading to an expanding or diverging outlet portion so that at least therequisite flow velocity is maintained within the throat portion foravoiding flashback over a relatively wide range of gas flow rates.Combustion of gases within the expanding portion of the orificesprevents lift off of the flame front in all operating conditions andwill heat portions of the ceramic plate to incandescence to form radiantheat. By supplying the combustible gas to burners of this type atrelatively high mass flow rates, with a powered air supply or blower, asdisclosed in commonly assigned copending U.S. Pat. application Ser. No.116,192, filed Feb. 17, 1971, the disclosure of which application isalso incorporated herein by reference, a blue flame operating mode isachieved wherein a stable blue flame flame front is formed on the entiresurface of the burner plate which can be modulated to produce heatoutputs of up to 2,000,000 BTUs per hour per square foot of surface.This output is substantially above that total available with theinfrared mode of operation of the burner plate and thus a greater totalheat output is achieved from the combustible gases and the same burnerplate so that the capacity of the fluid heater can be increased withoutany substantial increase in size. Moreover, it is contemplated that thecapacity can be varied by simply modulating combustion through theburner plate to increase its heat output and increasing the number ofheat exchanger tubes utilized.

Typically, pool water is supplied to the heater of this inventionthrough a control bypass valve which maintains the desired flow of waterthrough the heat exchanger and bypasses any surplus water from the poolfiltration system back to the pool.

The construction of the preferred embodiment of the present invention,as well as the advantages thereof will become further apparent from thefollowing specification when considered in conjunction with theaccompanying drawing wherein:

FIG. 1 is a perspective view of one embodiment of the swimming poolheater of the present invention showing the front and one side thereof;

FIG. 2 is a perspective view similar to FIG. 1 showing the rear and theother side of the heater;

FIG. 3 is a sectional view of the heater of FIG. 1, with parts brokenaway, taken on line 3-3 of FIG. 2;

FIG. 4 is a sectional view, with parts broken away, taken along line 4-4of FIG. 3;

FIG. 5 is a sectional view, taken along line 55 of FIG. 4;

FIG. 6 is a sectional view, similar to FIG. 3, of another embodiment ofthe invention;

FIG. 7 is a sectional view of the heater of FIG. 6, with parts brokenaway, taken along line 77 of FIG. 6; and

FIG. 8 is a partial sectional view, taken along line 88 of FIG. 6.

Referring now to the drawings in detail, and particularly to FIGS. 1 and2 thereof, there is illustrated a generally rectangular swimming poolheater 150, constructed in accordance with the present'invention andhaving an outer decorative housing 152 including front and rear wallpanels 154 and 156 respectively. The rear wall 156 of housing includesthree openings 20, 21 and 22 through which the various water and gaslines extend for connection with the heater components therein. Waterfrom the pools filter system is supplied through opening 20 to inlet 24of a manifold 160 and flows therefrom through a multiple tube heatexchanger 162 which extends between manifold 160 and manifold 164. Theheat exchanger illustrated in FIG. 4 is a four pass type which utilizestwo tubes 166 in each pass of the water flow from one manifold to theother;

however, it is noted that one, or more than two tubes,

may be used in each pass as desired. As illustrated, however, tubes 166are arranged in pairs and there are four pairs 168, 169, 170 and 172extending from rear manifold 160 to front manifold 1.64.

The ends of each of the tubes 166 are mounted in and suitably sealed to,their associated manifold. Manifold 164 includes a central wall 176which divides the manifold into two separate chambers 178 and 180,whereby chamber 178 connects the downstream end of the first pair oftubes 168 to the upstream end of the second pair 169, and chamber 180connects the downstream end of pair 170 with the upstream end of pair172.

Referring now to manifold 160, it is seen that this manifold includes aninterior wall 182 which separates the manifold into two sections 184 and186. Manifold section 184 provides a bypass passage for excess waterbypassed from heat exchanger 162 by a valve 40, positioned betweenmanifold inlet 24 and manifold section 186 at the entrance to heatexchanger 162, so that it is returned directly to the pool throughoutlet passage 36. The center portion of valve 40 includes conduitmember 42 which is connected to manifold 160 at one end adjacent theinlet 28 to manifold section 186, and has its free end 46 extending intoinlet 24. An annular valve member 48 is slidably mounted on conduit 42and includes an annular sealing surface 50 adapted to engage a matingvalve seat 52 on manifold 160 at inlet 24. Valve member 48 is biasedagainst seat 52 by a spring 54 in order to close the annular openingbetween conduit 42 and inlet 24.

In pool water heaters it is desirable to maintain a constant flow ofwater through the heat exchanger to prevent excessive lime build-upstherein, and valve 40 is provided to maintain this desired rate. Thus,the diameter of conduit 42 and the compression characteristics of spring54 are chosen to permit only the maximum desired flow rate into the heatexchanger so that when the total water flow from the filtration systemis equal to or below the desired flow rate through the heat exchanger,all water flow through conduit 42, and through tubes 168.

When the total water flow rate from the filtration system increasesabove the desired flow rate through the heater, the additional forceexerted by the increased flow of water against the tapered face 50 ofvalve member 48 moves it against the action of spring 54 away from itsseat 52. Thus, the additional water flowing into the unit bypasses valve40 and tubes 168 and flows directly through manifold section 184 tooutlet 36 where it is mixed with heated water from the heat exchanger162 and returned to the swimming pool. Spring 54 is designed to maintainvalve member 48 on its seat if the total water flow rate from thefiltration system is equal to or less than the desired flow rate throughthe heater coil.

Manifold section 186 provides intercommunication between the varioustubes 166 and is provided with a pair of integral partition walls 190which divide the section into chambers 192, 194 and 196. Water enteringinlet opening 24 of manifold 160 communicates with chamber 192 throughvalve 40 and at most only the maximum desired flow rate enters chamber192 through conduit 42. The water in chamber 192 is in directcommunication with the inlet ends of the pair of heat exchange tubes1'68 and flows through these tubes in the first pass across the heaterto chamber 178 in manifold 164. The water is returned from chamber 178on its second pass through conduit 169 to chamber 194 where it is incommunication with the inlet ends of the third pair of tubes 170. Atthe'end of the third pass, the water flows from chamber 180 throughtubes 172 to chamber 196 where it is discharged through opening 198 intomanifold section 184 and returned through outlet 36 to the pool.

Heat exchanger 162 is mounted in an intermediate portion of housingdirectly below planar heating unit 210. Heater unit 210 includes agenerally rectangular plenum chamber 212 which corresponds substantiallyin size to the heat exchanger, 162. An apertured ceramic burner plate214, more fully described hereinafter, is provided as the base of plenum212. A combustible mixture of gas and air is supplied to plenum chamber212 through duct 216 from powered blower 218 and a gas supply line (notshown). The air required for combustion is drawn by fan 218 through anopening 220 which is formed in front panel 154 and is provided with adeflector plate 222, thereby eliminating unsightly flues and ducts.

Burner plate 214 is provided with a plurality of venturi-like apertures220 having a generally cylindrical inlet throat port 78 and an expandingoutlet portion 82 on its outer face 224 opposite the upper surfaces oftubes 166. As disclosed in the above-mentioned US. Pat. application Ser.No. 116,192, in burner plates of this type, with relatively high massflow rates as provided when combustion air is supplied from a poweredblower with the combustible fuel, a laminar flow is established inthroat portion 78 which is projected into diverging outlet portion 82 asa central jet which separates from the surface of outlet portion 82 soas to create a relatively high velocity turbulent recirculating flowaround the central laminar flow or jet.

The diverging outlet portions of the orifices define edges along thesurface of the burner plate and as the jet of gas passes out of theorifices adjacent the surface edges a second turbulent recirculatingflow is produced at the surface of the plate as the jet separates at thedownstream side of the plate and the velocities of the high velocityturbulent flow are decreased as the turbulent flow moves over the edges.The resulting turbulent flow at the surface of the plate provides aself-igniting or piloting action for igniting the air-gas mixtureissuing from the diverging portion of the orifice to insure thatcombustion will occur along the surface of the plate rather than at alocation within the diverging portion of the orifices at the high massflow rate produced by the powered blower arrangement. As a result, ablue flame front, having a relatively short flame length, (less than 1inch, and typically between one-eighth inch and onehalf inch) isproduced on the surface of the plate. It has been found that the heatoutput of such a burner plate, operated in this manner will be from200,000 to 2,000,000 BTUs per hour per square foot of surface area. Thisrepresents a substantial increase in the amount of heat output and rangeof heat modulation, as compared to previously proposed conventional gasburners and infrared gas burners. Thus, the heat produced by a givenarea of burner plate is greatly increased and, as a result, the heaterunit of the present invention may be made substantially smaller thanother known swimming pool heater units. It is noted that in order toinitially ignite the flowing gases, a spark or glow coil ignition system(not shown) is provided in the preferred embodiments in lieu ofconventional pilot lights since the latter may readily be blown outunder high winds when the heater is used for outdoor pools.

The heat produced by burner plate 214 is directed downwardly towardtubes 166 to heat the tubes and the water flowing therein. These tubes,as seen in FIGS. 3 and 5, are spaced from each other and are providedwith radiating fins which are adapted to absorb heat by convection fromthe products of combustion formed as a result of the combustion inburner 214, which products are discharged downwardly upon and throughthe spacing between the tubes. It is noted that tubes 166 may beprovided with other known types of surface extensions in lieu of fins inorder to enhance heat transfer. In addition, because of the relativelyshort flame lengths occurring with the operation of burner plate 214,the exchanger can be located extremely close (approximately one inch) tothe burner plate so that the heat is applied directly to the heatexchanger tubes with little loss of heat by conduction through the wallsof the heater between the burner plate and the heat exchanger. As aresult, the present fluid heater can be made 60 percent smaller in sizethan conventionally proposed swimming pool heaters. Moreover, becausethe plate 214 is above heat exchanger 160, any condensation forming inthe heater will form on the relatively cool tubes 166 as the hot gasespass through; this condensate falls from the tubes to the base 240 ofhousing 150 which is sloped to direct the moisture to a drain 242 fordischarge. As a result, no condensate will drip upon the burner plate,as occurs with previously proposed fluid heaters, and thus the heater isstill more efficient for that reason. Because condensation forming onthe heat exchanger tubes does not affect the operation of the burner,the water flow rates through the heat exchanger can be increased,resulting in increased heater efficiency and preventing build-up of limedeposits in the heat exchanger tubes.

A plurality of generally inverted T-shaped deflectors 230 are mountedbelow tubes 166 downstream of the flow of products of combustion whichdeflects the hot gases around the bottom portion of the tubes toincrease distribution of the gases and effect an increased and moreuniform transfer of convective heat therefrom. While deflectors 230 havebeen illustrated as T- shaped members, it is noted that other deflectorshapes may also be utilized, and in particular it is foreseen that flator curved plate members will provide satisfactory deflection of gases.

After the products of combustion pass between deflectors 230 they flowdownwardly into discharge chamber 232 immediately below heat exchanger162. Chamber 232 is thermally insulated at its sides and front by plates234 to conserve heat and effect maximum heat transfer by convection totubes 162. However, the rear portion of chamber 232 is open to permitthe escape of the relatively cooled exhaust gases through an opening 236having a deflector 238 in rear wall 156.

In operation the heater is adapted to function automatically when thepool pump is in operation and is provided with a conventional thermostator aquastat (not shown) which senses inlet water temperature. If thewater temperature is below the desired minimum temperature, the fan orblower 218 is turned on by conventional control means and when it is upto speed, the electric gas valve and ignition system are actuated tostart the burner and heat pool water flowing through valve 40 and tubes168. A flame proving system (not shown) is provided to detect ignitionand shut down the burner on failure of the burner to ignite. Inaddition, a high limit temperature switch in the outlet 36 of manifold160 may be provided to prevent overheating of the unit in the event ofinsufficient water flow and a timer can be incorporated with blower 218to cool the unit after the burner shuts off and thereby reduce the limebuild-up in the heat exchanger.

An important feature of the present construction, particularly the useof the powered blue flame burner arrangement, is the fact that the heatoutput of the burner can be modulated over a wide range up to at least2,000,000 BTU s per hour per square foot so that the capacity of thefluid heater can be readily varied. It has been found that the heatoutput of the heater can be increased by increments of 250,000 BTUs perhour simply by increasing the number of ports on the burner plate, usinga larger blower and providing one additional row of heat exchanger tubes162 for each 250,000 increment desired. Thus, for example by adding asingle row of additional heat exchangers, as illustrated in FIGS. 6-8,the capacity of the heater is approximately doubled while the physicalsize of the heater is increased only approximately 15 percent. As aresult, the present invention permits the construction of a family ofswimming pool heaters which can be constructed in a modular mannerutilizing the same basic heat exchanger tubing module (i.e. the layersof tubes 168-472 and manifold 164), controls, burner tile and burnerplenum.

For example, the smallest heater in the family, a 250,000 BTU/hr.heater, would use a single heat exchanger module comprising tubes168-172 and manifold 164, a small combustion air blower, and the ceramicburner plate (which is the same plate in all cases) would simply have aportion of the orifices therein blocked in order to reduce the totalport area. For the next larger fluid heater, i.e. a 500,000 BTU/hr.heater, a second heat exchanger module, a larger combustion air blower,and the burner plate with its normal number of ports would be utilized.Further increased capacity heaters can be made by simply using anadditional heat exchanger module and a larger blower for each 250,000BTU increment desired. For each of such increments it has been foundthat a 15 percent increase in the physical size of the appliance isrequired to accommodate the larger blower and additional heat exchanger.However, it is to be noted that this increased size obtains asubstantial increase in capacity. For example, a 1,000,000 BTU/hr.heater has a capacity 300 percent greater than the smallest or 250,000BTU/hr. heater, with only a 50 to percent increase in size. It is alsonoted that the above heater outputs are exemplary only, since thespecific output of the heaters will vary in accordance with the size ofthe burner plate selected for use in a given family of heaters.Accordingly, it is seenthat by the disclosed heater construction a veryefficient and compact family of fluid heaters are provided which achievesubstantial production economies for the manufacturer because of thehigh degree of component commonality between the various heaters in agiven family of heaters.

Referring specifically now to FIGS. 6-8 of the drawing, there isillustrated a fluid heater from a family of heaters, in which anadditional layer or row of heat ex changer tubes 166' are provided,along with a larger capacity blower to double the output capacity of theheater as compared to that of the embodiment shown in FIGS. l-5. Thestructure, function and operation of the heater of this embodiment is:similar to the previously described embodiment, and accordingly,numerals applied to the elements of the prior embodiment are utilizedbelow to indicate like parts.

The additional heat exchanger 162 is identical to heat exchanger 162 andincludes a plurality of heat exchanger tubes 166 arranged in pairs 168',169, 170 and 172 extending from and being suitably sealed to a rearmanifold 164' and a front manifold 160. Manifold 164 is identical topreviously described manifold 164 but manifold 160 is modified somewhatfrom manifold 160 in order to accommodate the additional row of heatexchanger tubes. As seen in FIG. 7, chamber 192 is isolated from chamber184 by a wall 197. Thus, the water from the swimming pool, (which entersmanifold 160 and upper heat exchanger 162 in the same manner as in thepreviously described embodiment) flows through heat exchanger tube pairs168, 169, 170 and 172 in the manner indicated by the arrows in FIG. 7,into chamber 196 and from there (FIG. 6) flows into the lower pair oftubes 172'. The water flows through tubes 172, 170' 169, 168' in areverse direction from the flow of water in the heat exchangers and isdischarged into chamber 184 of manifold 160 at the ends of the pairs 168of heat exchanger tubes. From there the water is returned to the poolthrough outlet 36.

As in the prior embodiment, the upper layer 162 of heat exchanger tubesare located relatively close to the burner plate 214 so as to receiveheat directly from the burner with less attendant heat loss through thewalls of the heater between the burner and the heat exchanger. Thesecond layer 162 of heat exchanger tubes are mounted in closerelationship to the first layer. Typically, these tubes have a diameterof approximately l% inches and are mounted 2 inches on center.

As seen in FIG. 8, the tubes 166 and 166' are mounted in verticalalignment with cross-shaped deflectors 230' therebetween. Thesedeflectors deflect the hot gases around the bottoms and sides of tubes166 and along the tops and sides of tubes 166' to increase distributionof the hot gases and effect an increased and more uniform transfer ofconvective heat therefrom. Inverted T-shaped deflectors 230 are providedbelow tubes 166 for the same purpose. Alternatively, it is contemplatedthat the tubes 166' can be staggered with respect to tubes 166, i.e.located between and below tubes 166, so that deflectors 230' may beomitted.

The operation of this embodiment of the fluid heater is substantiallythe same as heater 150 previously described and thus need not bedescribed in detail.

It is thus seen that the first described embodiment of the invention isreadily modified to increase its capac ity. To further increase thatcapacity, all that is required is the provision of an additional layeror layers of heat exchanger tubes, a larger blower and a slightmodification in the construction of manifold 160, as would be clear toone skilled in the art in view of the above description.

Although the illustrative embodiments of the invention have beendescribed herein with reference to the accompanying drawings and forheating water for swimming pools, it is to be understood that theinvention is not limited to that field of use or to the preciseembodiments described herein, and that other fluids may be heated andthat various changes and modifications may be effected therein by oneskilled in the art without departing from the true scope or spirit ofthis invention.

What is claimed is:

1. A fluid heating device in the fluid flow path of a water circulationsystem comprising, a heat transfer conduit forming a portion of saidfluid flow path, a powered gas burner located closely adjacent saidconduit and adapted to supply heat directly to said conduit to heat thewater flowing therein upon combustion of fuel in said burner, agenerally airtight housing adapted to contain said conduit and saidburner, said housing including an exhaust opening adapted to dischargeproducts of combustion formed by said gas burner, whereby said housingand said conduit cooperate to define a flow path in said housing forsaid products of combustion whereby heat is provided to said conduit byconvection from said products of combustion.

2. A device as defined in claim 1 wherein said powered gas burnerincludes a burner plate having a plurality of orifices extendingtherethrough, each of said orifices including a throat portion ofrelatively small cross section extending from an inlet at one surface ofsaid plate and an expanding outlet portion extending from said throatportion to an opening at an opposite surface of the plate opposite saidcoil and having cross-sections increasing from said throat portion tosaid opening.

3. A device as defined in claim 2 including, means for supplying acombustible air-gas mixture to said one surface of said plates forpassage through said orifices at a mass flow rate such that there isestablished a central jet of said mixture through each of said orificesfrom said throat portion towards said outlet portion, a relatively highvelocity turbulent zone of air-gas mixture between said jet and thewalls of said orifice, and flow separation of said jet and said highvelocity turbulent zone of said air-gas mixture at the edge portion ofthe outlet openings of said orifice outlet portions, to provide a zoneof turbulent, low velocity recirculating flow along the surface of saidplate in which substantially unrestricted flame propagation occurs.

4. A device as defined in claim 3 wherein said housing is thermallyinsulated along the exterior thereof whereby a substantial portion ofthe heat from said products of combustion is transferred to heattransfer conduit by convection and heat loss through said housing isavoided.

5. A device as defined in claim 4 wherein said housing includes a secondopening through which condensate forming on said heat transfer conduitis discharged.

6. A device as defined in claim 1 wherein said burner is positionedadjacent the upper portion of said housing and includes, a base memberadapted to produce high intensity heat upon combustion of gases withinthe burner, said conduit including a plurality of heat transfer ductsoperably interconnected for fluid communication therebetween, said ductsbeing located below said base member to receive heat therefrom.

7. A device as defined in claim 6 wherein said heat transfer ductscomprise spaced finned members whereby the products of combustion fromsaid burner flow between and around said ducts prior to dischargethrough said exhaust opening.

8. A device as defined in claim 7 including, a plurality of deflectionplates mounted in said housing below said heat transfer ducts to deflectcombustion products flowing between said ducts to effect substantiallyuniform convective heating of said ducts by said products of combustion.

9. A device as defined in claim 7 wherein said base member comprises, aburner plate having a plurality of orifices extending therethrough, eachof said orifices including a throat portion of relatively smallcrosssection extending from an inlet at one surface of said plate and anexpanding outlet portion extending from said throat portion to anopening at an opposite surface of the plate opposite said heat transferducts and having cross-sections increasing from said throat portion tosaid opening.

10. A device as defined in claim 9 including, means for supplying acombustible air-gas mixture to said one surface of said plate forpassage through said orifices at a mass flow rate such that there isestablished a central jet of said mixture through each of said orificesfrom said throat portion towards said outlet portion, a relatively highvelocity turbulent zone of air-gas mixture between said jet and thewalls of said orifice, and flow separation of said jet and said highvelocity turbulent zone of said air-gas mixture at the edge portion ofthe outlet openings of said orifice outlet portions, to provide a zoneof turbulent, low velocity recirculating flow along the surface of saidplate in which substantially unrestricted flame propagation occurs.

11. A device as defined in claim 10 wherein said means is a poweredblower.

12. A fluid heating device comprising, a substantially airtight housing,powered gas burner means in said housing for producing high intensityblue flame heat therein positioned adjacent the upper portion of saidhousing, said powered gas burner means including a powered blower forsupplying a combustible air-gas mixture to the burner and a base memberadapted to produce high intensity blue flame heat upon combustion ofgases within the burner, means defining a flow path for said fluidthrough said device closely adjacent said bumer means whereby said fluidis heated by said high intensity heat, said means defining a fluid flowpath including a plurality of heat transfer ducts operablyinterconnected for fluid communication therebetween, said ducts beinglocated below said base member and closely adjacent thereto to receivesaid high intensity heat directly from said burner, said housing havingan exhaust opening therein for the products of combustion formed in saidburner and confining said products of combustion prior to dischargethrough said opening adjacent said flow path defining means to supplyheat to said fluid by convection.

13. A fluid heating device comprising, an insulated housing defining aheating chamber therein, powered gas burner means mounted within saidchamber adjacent the top of said housing and having an aperturedsubstantially planar base portion adapted to produce high intensity blueflame heat in said chamber upon combustion of gases adjacent saidapertures, a plurality of generally elongated tubular heat transferducts mounted within said housing below but closely adjacent said burnerand receiving said high intensity heat therefrom, said heat transferducts being connected in liquid communication with each other to providea flow path for said water and defining an exhaust chamber with the baseof said housing, said exhaust chamber having an exhaust opening thereinadapted to provide communication between said exhaust chamber and theatmosphere, whereby products of combustion from said burner flowdownwardly through and around said coil members to said exhaust chamberand said exhaust opening to supply additional heat by convection to saidcoils and the water flowing therein.

14. A device as defined in claim 13 for heating water for a swimmingpool including, valve means operatively connected to one of said heattransfer ducts for supplying a predetermined volume flow of water tosaid ducts and bypassing excess water back to the pool.

15. A device as defined in claim. 13 including, a plurality ofdeflection plates mounted in said housing below said heat transfer ductsto deflect said products of combustion about said ducts prior todischarge from said housing to effect substantially uniform convectingheating of said ducts by said-products of combustion.

16. The device as defined in claim 13 wherein said heat transfer ductsare mounted in a plurality of layers in said housing.

17. The device as defined in claim 16 wherein the ducts in each of saidlayers are in vertical alignment.

. UNITED STATES PATENT OFFICE 1 CERTIFICATE OF CORRECTION Patent NO.3,73 +;o65 Dated May 22, 1973 Inventor s) Edward A Reid, Jr. andRoberfbj G Venendaal It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

- Claim 13; line 25, change "coil members to--heat transfer Signed andsealed this 27th day of November 1975.

SEAL I Attest: 1 I

EDWARD M.PLETCHER-,JR. RENE D. TEGTMEYER Attesting Officer ActingCommissioner of Patents PSCOMM'DC 60376-P69 w p.s. GOVERNMENT rnlfrrlggsOFFICE: I!" o-up-sy, 1

FQRM PO-105O (10 63)

1. A fluid heating device in the fluid flow path of a water circulationsystem comprising, a heat transfer conduit forming a portion of saidfluid flow path, a powered gas burner located closely adjacent saidconduit and adapted to supply heat directly to said conduit to heat thewater flowing therein upon combustion of fuel in said burner, agenerally airtight housing adapted to contain said conduit and saidburner, said housing including an exhaust opening adapted to dischargeproducts of combustion formed by said gas burner, whereby said housingand said conduit cooperate to define a flow path in said housing forsaid products of combustion whereby heat is provided to said conduit byconvection from said products of combustion.
 2. A device as defined inclaim 1 wherein said powered gas burner includes a burner plate having aplurality of orifices extending therethrough, each of said orificesincluding a throat portion of relatively small cross section extendingfrom an inlet at one surface of said plate and an expanding outletportion extending from said throat portion to an opening at an oppositesurface of the plate opposite said coil and having cross-sectionsincreasing from said throat portion to said opening.
 3. A device asdefined in claim 2 including, means for supplying a combustible air-gasmixture to said one surface of said plates for passage through saidorifices at a mass flow rate such that there is established a centraljet of said mixture through each of said orifices from said throatportion towards said outlet portion, a relatively high velocityturbulent zone of air-gas mixture between said jet and the walls of saidorifice, and flow separation of said jet and said high velocityturbulent zone of said air-gas mixture at the edge portion of the outletopenings of said orifice outlet portions, to provide a zone ofturbulent, low velocity recirculating flow along the surface of saidplate in which substantially unrestricted flamE propagation occurs.
 4. Adevice as defined in claim 3 wherein said housing is thermally insulatedalong the exterior thereof whereby a substantial portion of the heatfrom said products of combustion is transferred to heat transfer conduitby convection and heat loss through said housing is avoided.
 5. A deviceas defined in claim 4 wherein said housing includes a second openingthrough which condensate forming on said heat transfer conduit isdischarged.
 6. A device as defined in claim 1 wherein said burner ispositioned adjacent the upper portion of said housing and includes, abase member adapted to produce high intensity heat upon combustion ofgases within the burner, said conduit including a plurality of heattransfer ducts operably interconnected for fluid communicationtherebetween, said ducts being located below said base member to receiveheat therefrom.
 7. A device as defined in claim 6 wherein said heattransfer ducts comprise spaced finned members whereby the products ofcombustion from said burner flow between and around said ducts prior todischarge through said exhaust opening.
 8. A device as defined in claim7 including, a plurality of deflection plates mounted in said housingbelow said heat transfer ducts to deflect combustion products flowingbetween said ducts to effect substantially uniform convective heating ofsaid ducts by said products of combustion.
 9. A device as defined inclaim 7 wherein said base member comprises, a burner plate having aplurality of orifices extending therethrough, each of said orificesincluding a throat portion of relatively small cross-section extendingfrom an inlet at one surface of said plate and an expanding outletportion extending from said throat portion to an opening at an oppositesurface of the plate opposite said heat transfer ducts and havingcross-sections increasing from said throat portion to said opening. 10.A device as defined in claim 9 including, means for supplying acombustible air-gas mixture to said one surface of said plate forpassage through said orifices at a mass flow rate such that there isestablished a central jet of said mixture through each of said orificesfrom said throat portion towards said outlet portion, a relatively highvelocity turbulent zone of air-gas mixture between said jet and thewalls of said orifice, and flow separation of said jet and said highvelocity turbulent zone of said air-gas mixture at the edge portion ofthe outlet openings of said orifice outlet portions, to provide a zoneof turbulent, low velocity recirculating flow along the surface of saidplate in which substantially unrestricted flame propagation occurs. 11.A device as defined in claim 10 wherein said means is a powered blower.12. A fluid heating device comprising, a substantially airtight housing,powered gas burner means in said housing for producing high intensity''''blue flame'''' heat therein positioned adjacent the upper portion ofsaid housing, said powered gas burner means including a powered blowerfor supplying a combustible air-gas mixture to the burner and a basemember adapted to produce high intensity ''''blue flame'''' heat uponcombustion of gases within the burner, means defining a flow path forsaid fluid through said device closely adjacent said burner meanswhereby said fluid is heated by said high intensity heat, said meansdefining a fluid flow path including a plurality of heat transfer ductsoperably interconnected for fluid communication therebetween, said ductsbeing located below said base member and closely adjacent thereto toreceive said high intensity heat directly from said burner, said housinghaving an exhaust opening therein for the products of combustion formedin said burner and confining said products of combustion prior todischarge through said opening adjacent said flow path defining means tosupply heat to said fluid by convection.
 13. A fluid heating devicecomprising, an insulated housing defining a heating chamber therein,Powered gas burner means mounted within said chamber adjacent the top ofsaid housing and having an apertured substantially planar base portionadapted to produce high intensity ''''blue flame'''' heat in saidchamber upon combustion of gases adjacent said apertures, a plurality ofgenerally elongated tubular heat transfer ducts mounted within saidhousing below but closely adjacent said burner and receiving said highintensity heat therefrom, said heat transfer ducts being connected inliquid communication with each other to provide a flow path for saidwater and defining an exhaust chamber with the base of said housing,said exhaust chamber having an exhaust opening therein adapted toprovide communication between said exhaust chamber and the atmosphere,whereby products of combustion from said burner flow downwardly throughand around said coil members to said exhaust chamber and said exhaustopening to supply additional heat by convection to said coils and thewater flowing therein.
 14. A device as defined in claim 13 for heatingwater for a swimming pool including, valve means operatively connectedto one of said heat transfer ducts for supplying a predetermined volumeflow of water to said ducts and bypassing excess water back to the pool.15. A device as defined in claim 13 including, a plurality of deflectionplates mounted in said housing below said heat transfer ducts to deflectsaid products of combustion about said ducts prior to discharge fromsaid housing to effect substantially uniform convecting heating of saidducts by said products of combustion.
 16. The device as defined in claim13 wherein said heat transfer ducts are mounted in a plurality of layersin said housing.
 17. The device as defined in claim 16 wherein the ductsin each of said layers are in vertical alignment.